This paper estimates a reaction function with forward-looking time-varying parameters for changes in the Brazilian monetary policy under inflation targeting regime. As the policy rule has endogenous regressors, the conventional Kalman filter can t be applied. Thus, a two-step procedure of the type Heckman (1976) is used to estimate the hyperparameters consistent model. The results show that: i) there is strong empirical evidence of endogeneity of the regressors of monetary policy rule, ii) the expected interest rate was above 10% throughout the analysis period to an average of 11%; iii) response the Selic rate to inflation varies considerably throughout the period and has shown a declining trend, iv) the response of interest rates relative to inflation deviation from the target with the principle of Taylor; v) the coefficient of smoothing rate interest has been constant throughout the period; vi) that the BCB had in much of the period analyzed an aversion recession by allowing inflation above target.